Usnic acid is a good medication for human papilloma virus (HPV) treatment and as an oral hygiene agent with limited effectiveness. Antimicrobial activity of acetone, methanol and ethanol extracts of Usnea species were investigated in vitro for testing microorganisms where some of them cause diseases in human, animal and plant and produce toxins and promote food deterioration. Lichen synthesize numerous metabolites called lichen substances including aliphatic, cyclo aliphatic, aromatic and terpenic components. Mycobiont of lichen produce antimicrobial secondary metabolites that save many animals from disease causing pathogens.
Antibiotic properties of lichens are investigated a lot.24 Vartia reported antimicrobial properties of several lichens and antimicrobial activity of several lichens against gram-positive, gram-negative bacteria have been studied by different researchers . For new drug discovery the search for novel natural bioactive compounds is receiving attention as new strains of multiple drug resistant pathogens become resistant to previously prepared standard drugs less effective against the emerging.
25 Quisumbing (1951) earlier reported the medicinal properties of fruticose lichen Usnea philippina.26Manojlovicet al(2010)tested the biological activities of these lichens and other fruticose lichens e.g. Usnea sp.
,Ramalina sp.,and Stereocaulon sp.,and reported their inhibitory activities against Gram-positive bacteria such as Micrococcus pyogenes, Bacillus subtilis and acid-fast bacilli.They are also reported to produce secondary metabolites with antimicrobial activity. However, though lichens are the novel source of potential drugs, the biological potentiality of lichens are very less studied.
Interestingly, the latter is known to have acquired resistance against major anti-TB drugs due to incomplete or partial treatment and necessitates treatment with new antibiotics .The demand of bioactive secondary molecules search for novel bioactive secondary metabolites is of primary concern since infectious diseases are continuously emerging and re-emerging. For e.g.
Mycobacterium tuberculosii infects approximately 9 million new individuals every year with 1.7 million deaths annually.27